We often get inquiries from patients in the clinic: How much is the relationship between anti-sperm antibodies and infertility? We have been treated before but it turned positive again, what happened? In response to the above question, we will briefly talk about anti-sperm antibodies (ASAb). ASAb is a pathological product, but the exact cause of its production is still not well understood and is mainly related to the immune response. Anti-sperm antibodies may be present in both men and women, and ASAb may be present in male blood, female blood, male semen, and female cervical mucus. There is no ASAb in women, but when semen enters the female reproductive tract, the female immune system may consider sperm as a specific antigen under certain environmental conditions (especially when a woman has inflammation of the reproductive tract or damage to the reproductive system), and the immune system may initiate an immune response for protection purposes, resulting in the presence of ASAb in women. Why can men also have ASAb? It turns out that the male immune system may also treat sperm (e.g., aging, dead sperm, etc.) as an antigen and initiate its own immune response to produce antibodies. There are many methods to detect ASAb, and the commonly used methods include IBT (immunobead test), mixed antiglobulin reaction (MAR) test, ELISA, sperm agglutination and fixation test, and radiolabeled lectin test. It is now common to test male semen and female blood. After testing positive for ASAb, further sperm-cervical mucus penetration tests as well as post-coital tests (PCT) are often required to determine the extent of the effect of ASAb and the management options. A high concentration of ASAb may lead to sperm agglutination, which in turn may lead to reduced sperm motility, thus reducing the chance of conception; however, anti-sperm antibodies within the normal range do not usually significantly affect conception. After the concentration of ASAb is found to be too high, it can be treated with anti-inflammatory drugs and herbal medicines to clear the heat and detoxify the toxins, etc. After the concentration of ASAb turns negative (drops to the normal range), it usually will not turn positive in a short time, but it is possible that the concentration of ASAb may rise again due to some inflammation or injury in the body of the male or female partner. The mechanism of ASAb’s influence on sperm-egg union and embryo development is still not clear, so you do not need to worry too much, and you can just take appropriate treatment in time after finding high ASAb concentration.